Secondary Battery

Abstract

A secondary battery according to embodiments of the present disclosure comprises an electrode assembly, which comprises a cathode, an anode disposed opposite to the cathode, and a separation membrane disposed between the cathode and the anode, which is wound around a winding core. The cathode comprises a cathode current collector having a first surface and a second surface that face each other, a first cathode active material layer disposed on the first surface, and a second cathode active material layer disposed on the second surface. A loading amount gap between the first cathode active material layer and the second cathode active material layer, and a diameter of the winding core satisfy a predetermined relationship.

What is claimed is: 
     
         1 . A secondary battery comprising an electrode assembly which comprises a cathode, an anode disposed opposite to the cathode, and a separation membrane disposed between the cathode and the anode, which is wound around a winding core;
 wherein the cathode comprises:   a cathode current collector comprising a first surface and a second surface that face each other;   a first cathode active material layer disposed on the first surface; and   a second cathode active material layer disposed on the second surface,   wherein the secondary battery satisfies Equation 1:   
       
         
           
             
               
                 
                   
                     
                       Y 
                       = 
                       
                         
                           A 
                           ⁢ 
                           
                             X 
                             2 
                           
                         
                         - 
                         
                           B 
                           ⁢ 
                           X 
                         
                         + 
                         C 
                       
                     
                     ; 
                   
                 
                 
                   
                     [ 
                     
                       Equation 
                       ⁢ 
                           
                       1 
                     
                     ] 
                   
                 
               
             
           
         
         wherein X denotes a diameter of the winding core, Y denotes a loading amount gap defined by Equation 2, A is 0.0062 to 0.013, B is 0.1242 to 0.2622, and C is 0.943 to 1.9907; 
       
       
         
           
             
               
                 
                   
                     
                       Loading 
                       ⁢ 
                           
                       amount 
                       ⁢ 
                           
                       gap 
                       ⁢ 
                           
                       
                         ( 
                         
                           mg 
                           / 
                           
                             cm 
                             2 
                           
                         
                         ) 
                       
                     
                     = 
                     
                       
                         LW 
                         ⁢ 
                         2 
                       
                       - 
                       
                         LW 
                         ⁢ 
                         1 
                       
                     
                   
                 
                 
                   
                     [ 
                     
                       Equation 
                       ⁢ 
                           
                       2 
                     
                     ] 
                   
                 
               
             
           
         
         wherein LW1 denotes a loading amount (mg/cm 2 ) of the first cathode active material layer, and LW2 denotes a loading amount (mg/cm 2 ) of the second cathode active material layer. 
       
     
     
         2 . The secondary battery according to  claim 1 , wherein the first cathode active material layer is positioned closer to the winding core than the second cathode active material layer. 
     
     
         3 . The secondary battery according to  claim 1 , wherein X in Equation 1 is 3 mm to 8 mm. 
     
     
         4 . The secondary battery according to  claim 1 , wherein the loading amount gap is 0.3 mg/cm 2  to 1.1 mg/cm 2 . 
     
     
         5 . The secondary battery according to  claim 1 , wherein the loading amount gap is 0.45 mg/cm 2  to 0.8 mg/cm 2 . 
     
     
         6 . The secondary battery according to  claim 1 , wherein LW1 in Equation 2 is 7.6 mg/cm 2  to 49.6 mg/cm 2 . 
     
     
         7 . The secondary battery according to  claim 1 , wherein LW2 in Equation 2 is 8 mg/cm 2  to 50 mg/cm 2 . 
     
     
         8 . The secondary battery according to  claim 1 , wherein an overall density of the first cathode active material layer and the second cathode active material layer is 3.2 g/cm 3  to 3.8 g/cm 3 . 
     
     
         9 . The secondary battery according to  claim 1 , wherein an average of LW1 and LW2 of Equation 2 is 16 mg/cm 2  to 30 mg/cm 2 . 
     
     
         10 . The secondary battery according to  claim 1 , further comprising a case in which the electrode assembly is accommodated. 
     
     
         11 . The secondary battery according to  claim 10 , wherein the case has a cylindrical shape. 
     
     
         12 . The secondary battery according to  claim 1 , wherein the electrode assembly comprises a jelly roll structure repeatedly wound around the winding core.